Page 259 - Textbook of Pathology, 6th Edition

produced by microwaves (ovens, radars, diathermy) or acid, B /pantothenic acid, B /pyridoxine, folate/folic acid, 243
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ultrasound waves used for diagnostic purposes do not B / cyanocobalamin, choline, biotin, and flavonoids).
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produce ionisation and thus are not known to cause any Vitamin deficiencies result in individual deficiency
tissue injury. syndromes, or may be part of a multiple deficiency state.
6. Minerals. A number of minerals like iron, calcium, phos-
NUTRITIONAL DISEASES phorus and certain trace elements (e.g. zinc, copper, CHAPTER 9
selenium, iodine, chlorine, sodium, potassium, magnesium,
Nutritional status of a society varies according to the socio-
economic conditions. In the Western world, nutritional manganese, cobalt, molybdenum etc) are essential for health.
imbalance is more often a problem accounting for increased Their deficiencies result in a variety of lesions and deficiency
frequency of obesity, while in developing countries of Africa, syndromes.
Asia and South America, chronic malnutrition is a serious 7. Water. Water intake is essential to cover the losses in
health problem, particularly in children. faeces, urine, exhalation and insensible loss so as to avoid
Before describing the nutritional diseases, it is essential under- or over-hydration. Although body’s water needs
to know the components of normal and adequate nutrition. varies according to physical activities and weather
For good health, humans require energy-providing nutrients conditions, average requirement of water is 1.0-1.5 ml water/
(proteins, fats and carbohydrates), vitamins, minerals, water Kcal of energy spent. Infants and pregnant women have
and some non-essential nutrients. relatively higher requirements of water.

1. Energy. The requirement of energy by the body is 8. Non-essential nutrients. Dietary fibre composed of
calculated in Kcal per day. In order to retain stable weight cellulose, hemicellulose and pectin, though considered non- Environmental and Nutritional Diseases
and undertake day-to-day activities, the energy intake must essential, are important due to their beneficial effects in
match the energy output. The average requirement of energy lowering the risk of colonic cancer, diabetes and coronary
for an individual is estimated by the formula: 900+10w for artery disease.
males, and 700+7w for females (where w stands for the
weight of the individual in kilograms). Since the requirement Pathogenesis of Deficiency Diseases
of energy varies according to the level of physical activities
performed by the person, the figure arrived at by the above The nutritional deficiency disease develops when the
formula is multiplied by: 1.2 for sedentary person, 1.4 for essential nutrients are not provided to the cells adequately.
moderately active person and 1.8 for very active person. The nutritional deficiency may be of 2 types:
1. Primary deficiency. This is due to either the lack or
2. Proteins. Dietary proteins provide the body with amino
acids for endogenous protein synthesis and are also a decreased amount of essential nutrients in diet.
metabolic fuel for energy (1 g of protein provides 4 Kcal). 2. Secondary or conditioned deficiency. Secondary or
Nine essential amino acids (histidine, isoleucine, leucine, lysine, conditioned deficiency is malnutrition occurring as a result
methionine/cystine, phenylalanine/tyrosine, theonine, of the various factors. These are as under:
tryptophan and valine) must be supplied by dietary intake i) Interference with ingestion e.g. in gastrointestinal disorders
as these cannot be synthesised in the body. The such as malabsorption syndrome, chronic alcoholism,
recommended average requirement of proteins for an adult neuropsychiatric illness, anorexia, food allergy, pregnancy.
is 0.6 g/kg of the desired weight per day. For a healthy ii) Interference with absorption e.g. in hypermotility of the gut,
person, 10-14% of caloric requirement should come from achlorhydria, biliary disease.
proteins. iii) Interference with utilisation e.g. in liver dysfunction,
3. Fats. Fats and fatty acids (in particular linolenic, linoleic malignancy, hypothyroidism.
and arachidonic acid) should comprise about 35% of diet. In iv) Increased excretion e.g. in lactation, perspiration, polyuria.
order to minimise the risk of atherosclerosis, poly- v) Increased nutritional demand e.g. in fever, pregnancy,
unsaturated fats should be limited to <10% of calories and lactation, hyperthyroidism.
saturated fats and trans-fats should comprise <10% of calories Irrespective of the type of nutritional deficiency (primary
while monounsaturated fats to constitute the remainder of or secondary), nutrient reserves in the tissues begin to get
fat intake (1 g of fat yields 9 Kcal). depleted, which initially result in biochemical alterations and
eventually lead to functional and morphological changes in
4. Carbohydrates. Dietary carbohydrates, are the major tissues and organs.
source of dietary calories, especially for the brain, RBCs and In the following pages, a brief account of nutritional imba-
muscles (1 g of carbohydrate provides 4 Kcal). At least 55% lance (viz. obesity) is followed by description of multiple or
of total caloric requirement should be derived from mixed deficiencies (e.g. starvation, protein-energy malnutrition)
carbohydrates. and individual nutrient deficiencies (e.g. vitamin deficiencies).

5. Vitamins. These are mainly derived from exogenous
dietary sources and are essential for maintaining the normal OBESITY
structure and function of cells. A healthy individual requires Dietary imbalance and overnutrition may lead to diseases
4 fat-soluble vitamins (A, D, E and K) and 11 water-soluble like obesity. Obesity is defined as an excess of adipose tissue that
vitamins (C, B /thiamine, B /riboflavin, B /niacin/nicotinic imparts health risk; a body weight of 20% excess over ideal weight
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